One size won't fit all

It's the learning platform discussion day today, as mentioned in this post. The more I have been thinking about a county wide learning platform, the more I think it won't work if it's a "one fit for all" option.
I'm going to put forward my views on a tiered system - ie full features for KS3 and above pupils, but a simple graphical interface for lower KS2 (and even KS1 if they are going that far).